Carbide, nitride and silicide enhancers for laser absorption

ABSTRACT

A compounded polymer material that can be laser marked is provided. The compounded polymer material includes an enhancer of nitrides, carbides, silicides, or combinations thereof. Upon forming the compounded polymer material into an article and exposing it to laser radiation, the irradiated portion of the compounded polymer material absorbs the laser radiation, increases in temperature, and forms a mark in the article. A lightness value difference (ΔL) between the mark and the non-irradiated portion of the article has an absolute value of at least 5, and the lightness value difference between the mark and the non-irradiated portion is greater than if the polymer material did not include the enhancer.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part application of U.S.application Ser. No. 15/877,427 filed Jan. 23, 2018, which is expresslyincorporated herein by reference.

FIELD

The present subject matter relates to laser marking compositions for usein laser marking operations and various methods of laser marking usingsuch compositions. The present subject matter also relates to articlesmarked using the noted marking compositions and/or methods.

BACKGROUND

Laser marking is a marking technique that uses lasers and other forms oflaser radiation to additively bond a marking substance to a wide rangeof substrates or to change the color of a particular substrate materialby chemical/molecular alteration, charring, forming, melting, etc. Lasermarking forms permanent marks on material such as metals, glass andceramic parts, and is used in many applications, ranging from aerospaceto awards and engraving industries. Laser marking differs from the morewidely known techniques of laser engraving and laser ablation in thatlaser marking is an additive process, adding material to the substrateto form the marking, or at least does not involve removing material fromthe marked substrate as in those techniques.

Individual laser bonding/marking compositions have had limited successwhen used to mark different types of substrate materials, and aretherefore classified according to the particular material to be marked.Instead, laser marking compositions are usually tailored for markingspecific types of material. For example, a single laser markingcomposition may leave a satisfactory laser mark on stainless steel, butmay leave an unsatisfactory mark on other materials such as differentgrades of aluminum, anodized aluminum, brass, copper, pewter, titanium,glass, ceramic, natural substances such as rock (e.g. slate) or paperproducts, and plastic. In order to mark on these other materials,different laser marking compositions have to be used than those used formarking stainless steel. Accordingly, there is a need for a highcontrast laser marking composition that can be used for marking avariety of materials.

Laser marking directly in a substrate comprising a polymer material, andnot involving the use of a marking composition, is limited by the levelof the polymer material itself to form a mark when irradiated with alaser. Accordingly, there is a need for forming higher contrasting marksin various polymer materials.

BRIEF DESCRIPTION

The difficulties and drawbacks associated with previously knownmaterials and practices are addressed in the present markingcompositions and methods for laser marking.

According to one aspect, a compounded polymer material comprising apolymer material compounded with an enhancer selected from the groupconsisting of nitrides, carbides, silicides, and combinations thereof.Upon exposing an irradiated portion of the compounded polymer materialto laser radiation, the irradiated portion absorbs the laser radiation,increases in temperature and forms a mark having a luminance, colorvalue, or degrees of opacity that provides visual contrast with anon-irradiated portion of the compounded polymer material. A lightnessvalue difference (ΔL) between the mark and the non-irradiated portionhas an absolute value of at least 5. The lightness value differencebetween the mark and the non-irradiated portion is greater than if thepolymer material did not include the enhancer.

According to another aspect, a method of producing laser marks includesproviding a polymer material and an enhancer selected from the groupconsisting of nitrides, carbides, silicides, and combinations thereof.The polymer material and the enhancer is compounded to produce acompounded polymer material. The compounded polymer material is formedinto an article having a desired configuration. At least a portion ofthe article is irradiated with laser radiation such that the irradiatedportion absorbs the laser radiation, increases in temperature, and formsa mark in the article that has a luminance, color, and/or degree ofopacity that contrasts with a non-irradiated portion of the article. Alightness value difference (ΔL) between the mark and the non-irradiatedportion has an absolute value of at least 5. The lightness valuedifference between the mark and the non-irradiated portion is greaterthan if the polymer material did not include the enhancer.

As will be realized, the present subject matter is capable of other anddifferent embodiments and its several details are capable ofmodifications in various respects, all without departing from thepresent subject matter. Accordingly, the drawings and description are tobe regarded as illustrative and not restrictive.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a photograph of several substrates laser marked with a markingcomposition in accordance with the present subject matter.

FIG. 2 is a photograph of several other substrates laser marked with amarking composition in accordance with the present subject matter.

FIG. 3 is a photograph of a plastic substrate laser marked with amarking composition in accordance with the present subject matter.

FIG. 4 is a photograph of a ceramic substrate laser marked with amarking composition in accordance with the present subject matter, andanother ceramic substrate marked with a comparative example markingcomposition.

FIG. 5 is a photograph of a glass substrate laser marked with a markingcomposition in accordance with the present subject matter, and anotherglass substrate marked with a comparative example marking composition.

FIG. 6 is a photograph of two glass substrates laser marked with markingcompositions in accordance with the present subject matter, and anotherglass substrate marked with a comparative example marking composition.

FIG. 7 is a photograph of a slate substrate laser marked with a markingcomposition in accordance with the present subject matter and markedwith a comparative example marking composition.

FIG. 8 is a photograph of an anodized aluminum substrate laser markedwith a comparative example marking composition.

FIG. 9 is a photograph of an anodized aluminum substrate laser markedwith a marking composition in accordance with the present subjectmatter.

FIG. 10 is a photograph of an aluminum substrate laser marked with amarking composition in accordance with the present subject matter, andanother aluminum substrate marked with a comparative example markingcomposition.

FIG. 11 is a photograph of a brass substrate laser marked with a markingcomposition in accordance with the present subject matter, and anotherbrass substrate marked with a comparative example marking composition.

FIG. 12 is a photograph of a stainless steel substrate laser marked witha marking composition in accordance with the present subject matter, andanother stainless steel substrate marked with a comparative examplemarking composition.

FIG. 13 is a photograph of a plastic substrate laser marked with amarking composition in accordance with the present subject matter, andanother plastic substrate marked with a comparative example markingcomposition.

FIG. 14 is a photograph of a ceramic substrate laser marked with amarking composition in accordance with the present subject matter, andmarked with a comparative example marking composition.

FIG. 15 is a screen shot of a colorimetry analysis of the markings ofFIG. 14.

FIG. 16 is a photograph of comparative example sheets of polymermaterials that have been laser marked.

FIG. 17 is a photograph of inventive example sheets of compoundedpolymer material that have been laser marked in accordance with thepresent subject matter.

FIG. 18 is a photograph of a comparative example film of polymermaterial that has been laser marked.

FIG. 19 is a photograph of inventive example films of polymer materialthat have been laser marked in accordance with the present subjectmatter.

FIG. 20 is a photograph of comparative example films of polymer materialthat have been laser marked and inventive example films of polymermaterial that have been laser marked and in accordance with the presentsubject matter.

DETAILED DESCRIPTION

The present subject matter relates to a universal or all-purpose lasermarking composition that, upon irradiation with a laser, leaves asatisfactory dark mark with high contrast on a variety of materialsincluding metal, glass, ceramic, natural substances, and plastic. Themetal substrates may include substrates made from, for example, regularand anodized steel, aluminum, brass, titanium, etc. The naturalsubstance substrates may include substrates made from, for example, claybricks, cellulose material, or stone such as slate. The plasticsubstrates may include substrates made from polymers such as, forexample, polycarbonate, acrylate, polyurethane, etc.

The invention of the present subject matter makes it possible to leave asatisfactory mark on a wide range of materials using a single markingcomposition, rather than having to use different laser markingcompositions tailored for each particular material to be marked.

The present subject matter provides various marking compositions,methods, and articles marked using the noted marking compositions andmethods. The marking compositions comprise one or more populations ofenhancers, which are included in the marking composition and allow themarking composition to leave satisfactory laser marks on a variety ofsubstrates. In accordance with the present subject matter, it has beendiscovered that certain aspects of the resulting marks can besignificantly improved or enhanced by selection and use of markingcompositions having the enhancers.

For example, surface bonding between the particles and the substrate canbe enhanced by use of the marking compositions having the describedenhancers. Generally, a darker, more contrasting laser mark results ifthe enhancer is included, irrespective of the substrate material. Thatis, by use of the described enhancer in a laser marking composition, anincrease in contrast in laser formed marks can be achieved at a broaderrange of power settings and scanning rates, i.e. at lower laser energiesand shorter times, to higher laser energies and longer times (i.e. atvarious time and power ratings). These and other advantages and benefitsare described in greater detail herein.

The enhancers of the present invention can also be compounded directlyinto polymer materials to be laser marked, which compounded polymermaterials can be formed into an article, such as a substantiallytwo-dimensional coating or film, or a three-dimensional object. Thearticle formed from the compounded polymer material can be directlylaser marked by irradiating the article with a laser. Laser marksproduced in this manner can contrast with the non-irradiated portion ofthe article more than if the enhancers were not included in thecompounded polymer materials.

Marking Compositions and Compounded Polymer Materials

As used herein, the term “marking composition” means a material that canbe disposed on a region of a substrate and irradiated by a laser toprovide an additive mark on the substrate that visually contrasts withthe substrate. In this regard, the mark is formed in an additive processon the substrate, wherein the mark is formed by adding material (i.e.the marking composition) to the substrate, rather than in a subtractiveprocess such as by laser ablation. As used herein, the term “compoundedpolymer material” means a material including a polymer material and anenhancer dispersed therein, that can be formed into an article having aparticular shape (sheet, coating, or three-dimensional object) and thendirectly irradiated by a laser to provide a mark within the articleitself. While not being bound to any particular theory, it is believedthat upon disposing the marking composition on a substrate and exposingthe marking composition to laser radiation, the marking compositionabsorbs the laser radiation, increases in temperature, and chemicallybonds with the substrate to form a fused mark on the substrate having aluminance, color value, or degrees of opacity that provides visualcontrast with the substrate. While not being bound to any particulartheory, it is believed that upon forming the compounded polymer materialinto an article and exposing the article to laser radiation, theirradiated portion of the article absorbs the laser radiation, increasesin temperature, and changes color through, for example but not limitedto, the polymer material undergoing chemical/molecular alteration orreaction, charring, forming, melting, bubbling, degassing etc. from theheat of the laser being absorbed by the enhancers to form a laser markin the compounded polymer material itself having a luminance, colorvalue, or degrees of opacity that provides visual contrast with thenon-irradiated portion of the compounded polymer material. The markingcomposition of the present subject matter are considered “universal” or“all-purpose” marking composition because when formed on variousmaterials, for example when formed on each of a metal, glass, ceramic,slate, and plastic substrates, the mark has a negative ΔL dark contrastvalue of at least −1, or −1 to −4, or −5 to −9, or −10 or more negative,when compared to a mark formed by a similar composition but without anenhancer selected from the group consisting of nitrides, carbides, andsilicides. When the mark has a negative ΔL value of at least −1, themark has visible contrast with a mark formed using similar compositionbut without an enhancer. When the mark has a negative ΔL value of −1 to−4, the mark has noticeable contrast with a mark formed using a similarcomposition but without an enhancer. When the mark has a negative ΔLvalue of −5 to −9, the mark has good contrast with a mark formed using asimilar composition but without an enhancer. When the mark has anegative ΔL value of −10 or more negative, the mark has significantcontrast with a mark formed using a similar composition but without anenhancer. When portions of the compounded polymer materials areirradiated with a laser, laser marks are produced that have an absolutevalue of ΔL of at least 5, 5-40, 7-35, 10-30, or 15-25 when compared tonon-irradiated portions of the compounded polymer materials. Inlight-colored compounded materials, the laser mark is darker than thecompounded polymer material; in dark-colored compounded materials, thelaser mark is lighter than the compounded polymer material.Additionally, laser marks formed in the compounded polymer materials aremore contrasting with the non-irradiated portions than laser marksformed in a similar polymer material that does not including theenhancers.

The resultant marked region contrasts with the non-irradiated region ofthe substrate or compounded polymer material, e.g., the marking may havea different (i.e. contrasting) luminance/lightness value and/or colorvalue on the Hunter Lab scale as compared with the non-irradiatedregion.

In the Hunter Lab scale, also CIELAB scale (so named for the variablesL, a, and b), L measures luminance or lightness and varies from 100 forperfect white to zero for black, approximately as the eye would evaluateit. Where DL=L (sample)−L (standard). If DL (which can also be expressedas ΔL) is positive, the sample is lighter than the standard. If DL isnegative, the sample is darker than the standard.

The chromaticity dimensions (a and b) give understandable designationsof color. The a dimension measures redness when positive, gray whenzero, and greenness when negative. Where Da=a(sample)−a(standard). If Da(or Δa) is positive, the sample is redder than the standard. If Da isnegative, the sample is greener than the standard.

The b dimension measures yellowness when positive, gray when zero, andblueness when negative. Where Db=b(sample)−b(standard). If Db (or Δb) ispositive, the sample is yellower than the standard. If db is negative,the sample is bluer than the standard.

The Hunter total color difference (DE or ΔE) for any illuminant orobserver is calculated as ΔE=√(ΔL²+Δa²Δb²).

The marking compositions may provide contrasting laser marks havingdifferent lightness values (L) as compared with the substrate lightnessvalue (L), thus providing a negative or positive lightness valuedifference (ΔL) between that of the substrate and that of the irradiatedmarking composition as determined by the standard CIELAB scale. Thecompounded polymer materials may provide contrasting laser marks havinga negative or positive lightness value difference (ΔL) between that ofthe non-irradiated and irradiated portions of the compounded polymermaterials. The marking compositions may provide contrasting laser markshaving different color values (a and b) than those of the substrate. Thecompounded polymer materials may provide contrasting laser marks havingdifferent color values (a and b) between those of the non-irradiated andirradiated portions of the compounded polymer materials. The markingcompositions may provide optimum color characteristics having certaindegrees of opaqueness to cover the laser marked portion of the substrateand provide contrast with the remaining portion of the substrate. Thecompounded polymer materials may provide laser marks that have optimumcolor characteristics having certain degrees of opaqueness that providecontrast between the irradiated and non-irradiated portions of thecompounded polymer materials. The marking compositions may provide lasermarks having lightness values, color values, degrees of transparency,translucence, opacity, and combinations thereof to provide contrast fromthe unmarked portion of the substrate. The compounded polymer materialsmay provide laser marks having lightness values, color values, degreesof transparency, translucence, opacity, and combinations thereof toprovide contrast between irradiated and non-irradiated portions of thecompounded polymer materials. The compounded polymer materials mayprovide laser marks having a total color difference (ΔE) with thenon-irradiated portions of from 5-35.

The resulting laser markings made in accordance with the present subjectmatter may need to be opaque for one application (such as in ceramicapplications), while another application the laser markings are colored,but may also have a certain degree of transparency or translucency toshow a certain effect on the substrate or in the article. The differencein lightness values ΔL between the marked and unmarked regions typicallyhas an absolute value of greater than about 10 as measured with a CIED65 illuminant at 10 degrees. The absolute value of ΔL is greater thanabout 20 in one embodiment, or greater than about 25 in anotherembodiment. In a particular embodiment, the absolute value of ΔL isabout 30 or higher. The laser markings made in accordance with thepresent subject matter and corresponding L, a, and b values for thosemarkings are measured with a spectrophotometer using a CIE D65illuminant at 10 degrees.

The opacity or opaqueness of a laser mark can be measured with aspectrophotometer over a black and white Leneta card. In one embodiment,the contrast measured over black and then white Leneta backgrounds forthe opacity of a laser mark is from about 1 ΔE to about 5 ΔE and inanother aspect from about 0.5 ΔE to about 2 ΔE.

Enhancer

The present subject matter laser marking compositions and compoundedpolymer materials generally comprise an enhancer selected from the groupconsisting of nitrides, carbides, and silicides. By “enhancer”, it ismeant the nitrides, carbides, and silicides, and also one or moreprecursors that when heated by laser irradiation produce the nitrides,carbides, or silicides. For example, an enhancer may include one or moreprecursors that react upon laser irradiation to form ferrosilicon(FeSi), which is represented in the following generic chemical reaction:A(Fe)+B(Si)→(FeSi)+C. In many of the marking compositions and thecompounded polymer materials described herein, more than one enhancer isprovided. For example, the marking compositions and the compoundedpolymer materials may include a first enhancer, a second enhancer, andstill additional enhancers.

The enhancer may include, but are not limited to, one or more offerromanganese (FeMn), (Co)Mo, CaSi, Cu₅Si, ferrosilicon (FeSi), Fe₅Si₂,MgFeSi, MnSi₂, MoSi₂, Ni₂Si, TiSi₂, ZrSi₂, WSi₂, YSi, Al₄O₃, boroncarbide (B₄C), CaC₂, Fe₃C, Fe₇C₃, Fe₂C, LaC₂, Mg₂C, Mg₂C₃, MoC, Mo₂C,Mo₃₀₂, SiC, Ta₄C₃, YC₂, WC, aluminum nitride (AlN), boron nitride (BN),Fe₂N, Fe₃N, Fe₄N, Fe₇N₃, Fe₁₆N₂, MoN, Mo₂N, silicon nitride (Si₃N₄),titanium nitride (TiN), W₂N, WN, WN₂, zirconium nitride (ZrN), andcombinations thereof, such as various stoichiometric alloys may also beemployed for example, in the case of Ferrosilicon Fe_(x)Si_((1-x)) whereX can range from about 0.005 to 0.995 typical alloy values may beX=0.85, X=0.55, X=0.25, or X=0.10. The enhancer may be included at 2-20wt %, 3-17 wt %, or 5-15 wt % of the laser marking composition and thecompounded polymer materials.

While not being bound to any particular theory, it is believed that theenhancer acts as a reducing or deoxidizing agent when irradiated withlaser radiation to provide an improved mark (darker, more contrasting)than compared to a laser marking composition and polymer materials notincluding the enhancer.

The laser marking compositions and compounded polymer materials may alsoinclude one or more of mixed metal oxide pigment, MoO₃, silicatemineral, binder, solvent, and dispersant.

Mixed Metal Oxide Pigment

The marking compositions or compounded polymer materials may include oneor more mixed metal oxide (MMO) pigments, also known as complexinorganic color pigments (CICP), for imparting a color to the lasermarking. Almost an infinite variety of colors can be achieved by usingdifferent and combinations of MMO pigments. MMO pigments are compoundsincluding at least two metals along with oxygen. MMO pigments includerutile, hematite, or spinel crystal structures. MMO pigments can includemetals such as cobalt, iron, chrome, tin, antimony, titanium, manganeseand aluminum. The MMO pigment may be produced by calcination attemperatures of 800° C. to 1300° C. of a mixture of metal precursormaterials.

The one or more MMO pigments may be included at 5-35 wt %, 15-30 wt %,or about 20-25 wt % of the marking compositions or compounded polymermaterials. The MMO pigment is not particularly limited, and in oneembodiment includes a cobalt-chromium-manganese-iron MMO pigment.Additionally, other coloring agents, such as pigments or dyes, can beused.

Silicate Mineral

In addition to other components, a silicate mineral(s) is optionallyadded to the marking compositions or compounded polymer materials toadjust rheological properties of and to provide durability for the lasermarkings in the marking compositions or for the compounded polymermaterials. The silicate material may be included at 1-15 wt %, 2-12 wt%, or 5-10 wt % of the marking composition or compounded polymermaterials.

Non-limiting examples of silicate minerals that can be used inaccordance with the present subject matter include phyllosilicatesselected from the serpentine group, the clay mineral group, the micagroup, and the chlorite group. In one embodiment, the markingcomposition includes mica or talc.

The particle size of the silicate minerals is not particularly limited,and the particles can have a median average particle size of about0.5-60 μm, 5-50 μm, 20-35 μm.

Transition Metal Oxide

The marking composition or compounded polymer materials can also includeone or more transition metal oxides, which provides laser absorbingsynergy to the marking compositions. The transition metal oxides may beincluded at 0.05-10 wt %, 1-9 wt %, or 3-8 wt % of the markingcomposition or compounded polymer materials.

Non-limiting examples of transition metal oxides that can be used inaccordance with the present subject matter include molybdenum oxide(MoO₃), and oxides of vanadium, manganese, iron, cobalt, nickel, copper,zinc, tungsten, titanium, chromium, and compounds and mixtures of these.In one embodiment, MoO₃ is included in the marking composition orcompounded polymer materials.

Binder

The marking compositions or compounded polymer materials of the presentsubject matter may comprise a binder to improve rheological properties,film formation, green strength, or package stability for the markingcompositions or compounded polymer materials. Binders may be included at0.01-5 wt %, 0.5-4 wt %, or 1-3 wt % of the marking compositions orcompounded polymer materials.

The binder may be dissolved in the solvent, and can include one or moreepoxies, polyesters, acrylics, cellulosics, vinyls, natural proteins,styrenes, polyalkyls, carbonates, rosins, rosin esters, alkyls, dryingoils, and polysaccharides such as starches, guar, dextrins andalginates, and the like, and derivative thereof. In one embodiment, thebinder includes hydroxypropyl cellulose.

Solvent

In accordance with the present subject matter one or more solvents areincorporated into the marking composition or compounded polymermaterials. The solvent can be included at 35-65 wt %, 40-60 wt %, or45-55 wt %. The solvents can comprise water or other aqueous-basedliquids, or one or more organic solvents. If water is selected as thecarrier, the water can be purified water, e.g. deionized water.

Non-limiting examples of other solvents include alcohols such asethanol. Non-limiting examples of organic solvents include ketones,alkanes such as butane (such as if in liquid form as a result ofpressurization such as may be used for spray applications), and aromaticorganic solvents such as xylenes.

In accordance with the present subject matter, the marking compositionsor compounded polymer materials may include solvents such as water,alcohols, polyols, chlorinated solvents, amines, esters, glycol ethers,ketones, terpenes, petroleum naphthas, aromatic hydrocarbons and naturaloils. Other suitable carriers include furans, isoparaffins, N,Ndimethylformamide, dimethylsulfoxide and tributylphosphine. In oneembodiment, the solvent includes ethanol.

Dispersant/Surfactant

One or more dispersants or surfactants can be included the markingcomposition or compounded polymer materials to aid in wetting,dispersing, and deflocculating the nitrides, carbides, and silicidesenhancer and other components of the marking composition or compoundedpolymer materials that are in particle form. In combination withparticle size optimization, the dispersant inhibits coalescing orclumping of the particles. If the particles are subjected to a particlesize reduction operation, the dispersant can be added during sizereduction to inhibit the particles from aggregating together to formlarger bodies. The dispersant can be included at 0.1-10 wt %, 1-8 wt %,or 2-5 wt %.

The dispersants are not particularly limited by the present subjectmatter. Examples of suitable dispersants include, but are not limitedto, Anti Terra 204, which is solution of a polycarboxylic acid salt ofpolyamine amides, and DISPERSBYK182, which is a solution of a highmolecular weight block copolymer with pigment-affinic groups, both ofwhich are supplied by BYK Additives and Instruments, Abelstraße 45,46483 Wesel, Germany.

Generally, any surface active dispersant, silicon based dispersant,etc., may be suitable for use in the marking compositions. Non-polymericand polymeric surface active dispersants, surfactants or agents can beincorporated into the formula.

Preparation of the marking composition in liquid form can, for example,occur through low shear mechanical mixing, high shear mechanical mixing,ultrasonic mixing and/or milling, or the like.

Depending upon the type of application technique, the components of themarking compositions will vary. For example, if a tape is beingproduced, the marking composition may comprise a considerable amount ofbinder. However, if a powder is being formed, such powder may be free ofbinder. Similarly, if a liquid application technique is being used, aconsiderable amount of solvent may be utilized, whereas with a powder,little or no solvent would be employed. One or more additionalcomponents may also be included.

The marking compositions or compounded polymer materials made inaccordance with the present subject matter can be formulated with feweror additional components in ways that makes them suitable for one ofmany application techniques depending upon the particular requirementsof the final marking process. For example, the marking compositions maybe incorporated into a powder, a tape or a liquid medium.

Additional Components

The marking compositions or compounded polymer materials may optionallyinclude one or more additional components (i.e. additives) generallyknown in the art to improve dispersability, wetting, flow and rheology,and to relieve surface defects.

The present subject matter marking compositions or compounded polymermaterials may incorporate these additional components depending on theintended application. Non-limiting examples of typical additives includeglass frits, glass frit precursors, metal oxides, metals, fluxes,oxidizers, reducers, coloring agents such as carbon black, viscosityadjusting agents, flow controllers, stabilizers, and clarity promotersto promote maintenance of optical characteristics of the markingcompositions. As noted, the use of one or more additives in the markingcompositions or compounded polymer materials is optional.

Examples of glass frits include those comprising alkali metal oxides,alkaline earth metal oxides, silica, boric oxide and transition metaloxides. In addition to glass frit, precursors of such glass fritmaterials may be used for the marking compositions or compounded polymermaterials. Examples of glass frit precursors include metal oxides withglass formers, such as silica, zinc oxide, bismuth oxide, sodium borate,sodium carbonate, feldspars, fluorides, and the like.

Marking Compositions

Generally, when using the marking compositions, the mark quality dependson a variety of factors, including the substrate used, marking speed,laser spot size, beam overlap, materials thickness, and laser operationparameters. The marking compositions may be applied to the substrate byvarious methods including a brush on technique, masking, dosing, wet anddry electrostatic deposition, dispensing, coating, metering, painting,spraying, dipping, water fall, pad printing, screen printing, rollcoating, tape, digital electronic deposition using such applicationtechniques as ink jet and valve jet application, and others.

The marking processes using the marking compositions generally comprisethree operations. One operation involves application of the markingcomposition to a substrate. Another operation involves bonding of themarking composition to the substrate with a laser. The laser used toform the laser marks is not particularly limited, and can comprise afiber laser, a CO₂ laser, diode laser, or other lasers. And, stillanother operation involves removal of excess, unbonded markingcomposition from the substrate in the cases where the applicationtechnique deposits excess material that is not subject to the laserenergy for making the desired mark.

In accordance with the present subject matter, a selected portion of themarking composition is permanently adhered to the substrate uponirradiation. As used herein, the term “adhere” is used to designate anypermanent means of attachment of the irradiated marking composition tothe substrate. For example, the irradiated marking composition may beadhered to the surface of the substrate by sintering the markingcomposition to the substrate, fusing the marking composition to thesurface of the substrate, diffusing at least a portion of the markingcomposition into the substrate, chemically bonding the markingcomposition with the substrate by chemical reaction, and the like. Inseveral embodiments, the marking composition is chemically bonded to thesubstrate.

As used herein, the term “permanent marking” means a non-temporarymarking which, for example, possesses relatively high wear resistance,corrosion resistance and/or fading resistance. While not being bound toany particular theory, it is believed that the interaction of the laserradiation and the marking composition results in an inert coatingmechanically and chemically bonded to the substrate material. Themarking composition is believed to form covalent bonds with thesubstrate material upon laser irradiation, and it is believed thischemical bond exceeds the strength of the mechanical bond.

Upon bonding of the marking composition to the substrate by exposure tolaser radiation, the resulting marking composition is fused to thesubstrate, and in most cases the marking composition is as durable asthe substrate itself.

Use of and/or the combination of different marking compositions, secondand/or subsequent applications of marking compositions and/or theadjustment of laser operation parameters will result in variations inthe durability, appearance, and structural form of the resulting lasermark and are part of the present subject matter. All of these markingcharacteristics can be achieved with the use of a single low-power,low-cost air-cooled diode laser.

Application of Marking Composition to Substrates

In a particular aspect, the present subject matter provides variousapplication methods for disposing the marking compositions to asubstrate.

The thickness of the resulting coating can be adjusted and/or controlledby the use of viscosity agents in the marking composition, by thecontrol of temperature, and by using optional treatments or pre-coatingson the surface to be marked. Depending upon the concentration of thecoloring agent(s) (MMO pigment) in the marking composition and otherfactors, adjusting the coating thickness can be used to at leastpartially control contrast or darkness of the markings. Typically,thickness of the coating will vary depending upon coating chemistry andheat stability. Marking compositions are typically applied to thesubstrate with a thickness of at least about 0.1 micron, alternativelyfrom about 1 to about 300 microns, or from about 5 to about 200 microns,or from about 10 to about 100 microns.

The present subject matter marking compositions can be disposed on asubstrate by different means depending on the requirements for differentapplications. The characteristics of the laser markings can be tailoredin part by altering the components of the marking compositions and inpart by selecting the appropriate method for applying the markingcompositions to a substrate.

In accordance with the present subject matter, the marking compositionsare in both solid (e.g. a dry powder or tape) and liquid (e.g. a slurry)forms.

In one aspect, the present subject matter comprises a solid markingcomposition in the form of a powder. Marking compositions in powder formcan be brought into contact with the substrate surface at the desiredthickness by solvent-less or low-solvent methods such as tape casting,powder deposition, powder dispensing, powder coating, powder metering,powder dosing, powder masking, powder painting, or the like.

In another aspect, the present subject matter comprises a markingcomposition in the form of a liquid. Water based methods may be usedbecause of their minimal environmental impact, but solvent based methodscan also be used to control drying rate, dispersion or moisturesensitivity of certain marking compositions. In accordance with oneembodiment, sol gel materials may be used to apply the markingcomposition to the substrate. Where dispersions are used, the depositedlayer of marking composition can be dried prior to being exposed tolaser radiation, however this is not necessary. The marking compositionin liquid form can be applied onto the substrate surface by variousmethods such as screen printing, painting, flood coating, brushing,spraying, roll coating, dipping, flow coating, electrostatic applicationand doctor blading.

In one aspect of the present subject matter, marking compositions inliquid form are coated in the form of a tape onto a surface of a carrierfilm. The marking composition can, for example, be in the form of atacky layer, arranged on a carrier film of polyester, polyethylene,polypropylene, or paper for example.

The marking compositions in tape form be disposed on a portion of asubstrate and the carrier film can be removed. The tape can betransparent, opaque, or translucent. The use of a tape insures properand uniform thickness and uniform distribution of components in themarking composition that is brought into contact with the substratesurface. It is not necessary that carrier film be used. It is alsocontemplated the carrier film need not be removed before laserirradiation, so long as the film does not interfere with the markingcomposition, and laser radiation can penetrate the thickness of the filmto reach the marking composition to produce markings on the surface ofinterest.

Additional materials used in the application of the marking compositionin liquid form or in the fabrication of tape may be substantiallyvaporized into combustion by-products and vented away from thesubstrate. A laminar air flow across the surface of the substrate can becreated by venting and/or exhausting equipment to insure a consistentlocalized environment in which the process can occur.

In another aspect, marking compositions are dispersed in hightemperature waxes or polymers in the form of a hot melt markingcomposition that is applied by heating the hot melt to liquid form andcoating the substrate with the liquid, or by rubbing the surface of thesubstrate with such hot melt material while in solid form.

Compounded Polymer Materials

The marking processes using the compounded polymer materials generallyinclude dispersing one or more enhancers in a polymer material toprepare the compounded polymer material, forming the compounded polymermaterial into an article, laser marking the article. The process mayalso include curing the compounded polymer material, which may occurbefore or after laser marking the article.

The polymer material is not particularly limited, and may includevarious thermoplastics or thermosets, including polyethylene,polypropylene, polystyrene, polyvinyl chloride, synthetic rubber, phenolformaldehyde resin (or Bakelite), neoprene, nylon, polyacrylonitrile,PVB, silicone, fluoropolymers, acrylics, polycarbonates, ethylene vinylacetate, etc., copolymers and homopolymers of these, and compounds andmixtures thereof.

The process of dispersing the enhancer in the polymer material is notparticularly limited, and may involve mixing the polymer material ineither melted or dry form along with the enhancer by using, for example,extruders, shakers, attritors, horizontal mills, immersion mills,two-roll mills, ball mills, grinders, spinners, blenders, mixers, etc.

Forming the Articles from the Compounded Polymer Materials

The process of forming an article from the compounded polymer materialsis not particularly limited, and may result in the formation of asubstantially two-dimensional sheet or coating, or of athree-dimensional object having a desired configuration. The formingprocess may include molding (e.g. injection, extrusion, blow, spin,rotational, or compression molding), forging, die casting, coating (e.g.wire, rod, doctor blade, or roll coating), roll forming, stamping,powder compaction, casting, spraying, dipping, or other forming methods.

Laser Marking

After the marking composition is applied to the surface of thesubstrate, or after the article is formed from the compounded polymermaterial, a selected portion of the marking composition or article isirradiated with a laser beam (i.e. laser radiation). Such irradiation tothe marking composition adheres the irradiated portion of the markingcomposition to the substrate and forms a permanent marking thereon. Suchirradiation to the article forms a permanent laser mark in the article.For many types of markings, the selected portion of the markingcomposition or article to be irradiated may comprise from about 1 toabout 99 percent of the total surface area of the layer of markingcomposition or article, typically from about 5 to about 95 percent. Inone embodiment, a laser is used to selectively irradiate the markingcomposition or article. However, other forms of focused energy may beused in accordance with the present subject matter. Irradiation may beachieved by moving a laser beam over a stationary substrate usingconventional beam steering methods, by moving the substrate in relationto the laser beam, and/or by masking the substrate. Laser irradiation istypically achieved by directing the laser beam directly against thelayer of marking composition or article, but may also be achieved bydirecting the beam through a sufficiently transparent substrate.

A wide array of lasers can be used for the present subject matter.Useful lasers for use in the present methods are those known as CO₂lasers, fiber lasers (e.g. YVO₄ laser), diode lasers, excimer lasers,green lasers, red lasers, UV lasers, and others.

A CO₂ laser produces a beam of infrared light with the principalwavelength bands centering around 9.4 and 10.6 micrometers. CO₂ lasersare available commercially from numerous sources. A suitable CO₂ laseris a 35 watt CO₂ laser with about 9.2 micron to about 11.4 micronwavelength.

A fiber laser is a laser in which the active gain medium is an opticalfiber doped with rare-earth elements such as erbium, ytterbium,neodymium, dysprosium, praseodymium, and thulium. They are related todoped fiber amplifiers, which provide light amplification withoutlasing. Fiber lasers are also commercially available from numeroussources. A suitable fiber laser is a 10 watt non-pulsed fiber laser withabout 904 nm to about 1065 nm wavelength.

Generally, the intensity of the laser and the particular wavelength orranges of wavelength(s) are selected based upon the characteristics ofthe marking composition or article, and the surface to be laser marked.Typical settings for a 35 watt CO₂ laser for universal laser markings isfrom about 2% to about 100% of full power at about 5 to about 100 inchesper second speeds. For most coatings, a power level from about 2% toabout 35% of full power at about 3 to about 100 inches per second speedsare used. A 10 watt fiber laser can be used from about 3 to 100 inchesper second speeds and the power can be from about 1 to about 10 watts.The term “speed” as used herein refers to the velocity of the markinghead as it moves across the surface being lased. The marking conditionswill vary from one laser to another and achieving a mark is not limitedto a particular laser. Changing to a higher or lower watt laser wouldchange the marking parameters, and so one could mark at a lower % powerand faster speed or vice versa. The particular combination of powersetting, marking speed, and other parameters for the laser of interestcan be determined by empirical testing to identify the optimum settings.

The actual power levels as measured at the surface to be marked areslightly different (more or less) than the power measurement of thelaser as delivered. As will be appreciated, this is primarily due to theefficiency of the laser tube. A wide array of other lasers can be usedsuch as YAG pulsed lasers, diode lasers, excimer lasers, green lasers,red lasers, UV laser and others.

In accordance with the present subject matter, the size of the laserspot that impinges the marking composition or article is typicallygreater than 0.1 micron in diameter, alternatively from about 0.1 toabout 20 microns, or from about 0.5 to about 10 microns. The speed atwhich the laser beam travels across the surface of the markingcomposition or article can range from 1 to about 100 inches/minute (upto about 250 cm/minute), alternatively from about 1 or 2 to about 20inches/minute (about 2.5 or 5 to 50 cm/minute) for most thicknesses andingredients of the marking composition or article. The laser beam may beprojected with a seam overlap of 1 to 100 percent, alternatively fromabout 10 to about 90 percent for many applications. The laser parametersare controlled in order to provide sufficient localized heating of themarking composition or article while avoiding unwanted damage to thesubstrate or article.

Once the marking composition is disposed on a portion of the substrateor once the article is formed from the compounded polymer material, thebeam emanating from the laser radiation source impinges upon the markingcomposition or article, which irradiated portion absorbs the laserradiation and increases to the required temperature. In absorbing thelaser radiation, at least a portion of the marking composition orarticle is excited, i.e. has its atoms or molecules raised to an excitedstate. [See Webster's Encyclopedic Unabridged Dictionary of the EnglishLanguage (Portland House, New York, 1989), page 497.] Typically, atemperature of 200° F. to 1500° F. is reached in approximately one totwo microseconds. Precise temperatures are controlled by the outputpower of the laser radiation source and the physical position of themarking composition or article relative to the focal plane of the laserradiation beam and the speed with which the beam is moving. Once therequired temperature is achieved, the marking composition and substratewill permanently bond together to form a new marking layer atop thesubstrate or the irradiated portion of the article itself will bemarked. Marking compositions or the articles can be formulated to absorbspecific amounts of a specified wavelength of the laser radiation.

The permanent markings produced in accordance with the present subjectmatter have a thickness of from 0.01 to about 100 microns as measuredfrom the surface of the substrate. In another aspect, the thickness isfrom about 0.05 to about 30 microns. In one aspect, substantially noindention or removal of the substrate is observed.

Several different methods are suitable for laser marking, for example:a) the mask method whereby the surface to be marked is uniformly coatedwith the marking composition or the article includes a uniformdispersion of enhancers, and the laser radiation is passed through afixed, data specific mask and the laser radiation therefore impingesonly the unmasked portions of the marking composition or article toproduce the desired mark; b) the dot-matrix method whereby the surfaceto be marked is uniformly coated with the marking composition or thearticle includes a uniform dispersion of enhancers, and the laserradiation passes through a computer controlled, changeable data,dot-matrix mask and impinges onto the marking composition to produce thedesired mark; c) the beam deflection method whereby the surface to bemarked is uniformly coated with the marking composition or the articleincludes a uniform dispersion of enhancers, and the laser radiationpasses through a beam steering head and impinges onto the markingcomposition or article to produce the desired mark; d) the X-Y plottermethod whereby the surface to be marked is uniformly coated with themarking composition or the article includes a uniform dispersion ofenhancers, and the laser radiation moves on a gantry type X-Y mechanismutilizing mirrors and/or fiber-optics and impinges onto the markingcomposition or article to produce the desired mark; e) the part movingmethod whereby the surface to be marked is uniformly coated with themarking composition or the article includes a uniform dispersion ofenhancers, and the workpiece to be marked is moved using an X-Y motordriven stage under a stationary beam which impinges onto the markingcomposition or article to produce the desired mark; and f) the areairradiation method whereby data specific marking composition isuniformly applied to the surface of the substrate or the articleincludes a uniform dispersion of enhancers, and the data specificmarking area is irradiated by means of a beam steering mechanism or bymeans of moving the workpiece under a stationary beam. In methods b),c), d), e) and f) the laser can be combined with a laser marking systemso that the marking composition or article can be irradiated with anycomputer programmed digits, letters and special symbols where the laserbeam strikes the marking composition or article in the most efficientmanner possible.

The laser beam, the movement of which can be controlled by a computer,may be used to create discrete symbols or designs or, alternatively, maybe serially indexed across the surface of the marking composition orarticle to create multiple symbols or designs at the same time. Forexample, a word may be created by separately making each letter of theword with the laser, or by rastering the laser across the entire word toform all of the letters at the same time.

During the irradiation step, the surface of the substrate or the articlemay be exposed to any desired type of atmosphere. For example, theatmosphere may comprise air at atmospheric, sub-atmospheric orsuper-atmospheric pressures. Furthermore, the atmosphere may comprise aninert gas such as nitrogen, argon or carbon dioxide, an oxidizingatmosphere such as air or oxygen, a reducing atmosphere such as hydrogenor carbon monoxide, or a vacuum.

Oxidizing or reducing gases can be used in a combination with inertgases. The atmosphere to which the surface of the substrate or thearticle is exposed may affect the color and the quality of the mark. Asingle laser beam may be used for marking in accordance with the presentsubject matter. Alternatively, two or more laser beams may be used.

Removal of Excess Marking Compositions from Substrates

The present subject matter methods involve removing the excess markingcomposition from the substrate. Excess marking composition not bonded tothe substrate surface can be removed by conventional cleaning processes.In high-volume applications, the unused marking composition can berecovered from the cleaning process and reused.

Removal of excess marking composition is accomplished depending on theform and application technique employed to deliver and apply the markingcomposition. For example, if the marking composition was in powder form,the excess powder that was not subject to laser irradiation can beremoved by wiping, dusting, washing, brushing off, vacuuming, sublimingor blowing off the substrate, or the like. On the other hand, if thearticle used to apply the marking composition was a tape carrier, thenthe portion of the tape that was not irradiated by the laser can bepeeled from the substrate. The irradiated portion of the markingcompositions remains adhered to the substrate forming a permanent mark.

The present subject matter methods enable formation of high contrast ordark marks on a portion of a substrate. High-contrast marks or darkmarks, for the purposes of this disclosure, means marks that are visibleto the human eye, and/or machine readable, and are darker than thesurrounding unmarked portions of the substrate. For example, ahigh-contrast or dark mark may appear on a transparent substrate to be ablack, brown, purple, blue, green or other high-contrast, dark orcolored mark.

After formation of a coating of the marking composition on the surfaceof interest, the coating and underlying surface is selectivelyirradiated with the noted source of energy, which in one embodimentcomprises a laser. The term “selective irradiating” refers to directinglaser radiation to only particular localized regions of the coating andunderlying surface. These regions correspond to the shape and outline ofthe desired marks. The laser is operated as previously described, i.e.at the noted power levels and speeds. The distance of the laser sourcefrom the surface to be marked varies depending upon the focal length ofthe laser beam. Typically, one or more lenses can be used to focus thelaser beam at 1.5, 2, and 4 inches from the surface for example. Formany marking applications, a distance of about 1.5 inches between thelens and the surface to be marked is appropriate for a CO₂ laser asdescribed herein.

Various types of marks may be produced in accordance with the presentsubject matter. For example, the marks may comprise alphanumericsymbols, graphics, logos, designs, decorations, serializations, barcodes, two dimensional matrices and the like. In addition, the markingsmay comprise three-dimensional lines forming patterns suitable for usein plasma display TV screens, fresnel lenses, polarizing filters,conductive circuits and the like.

In accordance with the present subject matter, permanent markings areformed with high contrast and high resolution. Resolution of the mark isdetermined, at least in part, by the size of the laser beam. Contrast ofthe mark from the substrate is typically determined, at least in part,by the laser beam energy, make up of the marking composition, andatmosphere in which the laser marking is performed.

Furthermore, by using conventional laser controlled hardware andsoftware, the markings of the present subject matter may be quicklyvaried from operation to operation for applications such asserialization, bars codes, manufacturing quality control and automatedmanufacturing.

Evaluations

A series of investigations was conducted in which laser marks formedusing inventive laser marking compositions and articles were contrastedwith laser marks formed from commercially available comparative markingcompositions and polymer materials not including the enhancers. Thelaser marks formed on various materials using the inventive markingcompositions and compounded polymer materials and the comparativemarking compositions and comparative polymer materials were compared asfollows.

Evaluation 1. This evaluation was performed by marking a glass substrateusing an inventive laser marking composition Inventive Example 1comprising 10 wt % FeSi enhancer and LMM6000, which is a commerciallyavailable laser marking composition formulated for stainless steel,available from Ferro Corporation, Mayfield Heights, Ohio. TheComparative Example 1 includes the same marking composition as Example1, but without 10 wt % FeSi enhancer. The laser marks were formed usinga universal 35 watt CO₂ laser. The laser settings for Inventive Example1 were 10P/10S, and for Comparative Example 1 were 25P/10S, whereinP=power in watts, and S=speed in inches per minute. The resulting lasermarkings on glass were evaluated for luminance and color value, and theevaluations are shown below in Table 1.

TABLE 1 Marking Composition L* a* b* DL* Da* Db* DE* Comparative 65.04−0.67 4.65 Example 1 Inventive 31.41 0.10 0.14 −33.62 0.77 −4.51 33.93Example 1

As can be seen, even though the LMM6000 marking composition isformulated for marking stainless steel, Example 1 including 10 wt % FeSienhancer produced a laser mark on glass that was 33.62 units darker(i.e. DL*) versus the laser mark produced by Comparative Example 1without enhancer.

Evaluation 2. This evaluation was performed by marking a ceramicsubstrate using Example 1 and Comparative Example 1. The laser markswere formed using a universal 35 watt CO₂ laser. The laser settings forInventive Example 1 were 20P/40S, and for Comparative Example 1 were20P/5S. The resulting laser markings on ceramic were evaluated forluminance and color value, and the evaluations are shown below in Table2.

TABLE 2 Marking Composition Strength L* a* b* DL* Da* Db* DE* Inventive51.5 0.55 4.27 Example 1 Comparative 100 61.6 3.74 9.91 10.1 3.19 5.6412 Example 1

As can be seen, Comparative Example 1 without enhancer produced a lasermark on ceramic that was 10.1 units lighter (i.e. DL*) versus the lasermark produced by Inventive Example 1 with the enhancer.

Evaluation 3. This evaluation was performed by marking a glass substrateusing an inventive marking composition Inventive Example 2, comprising10 wt % FeSi enhancer, 5-35 wt % mixed metal oxide pigment, 0.5-10 wt %transition metal oxide, 1-15 wt % silicate mineral, 0.1-5 wt % binder,35-65 wt % solvent, and 0.02-10 wt % dispersant. The Comparative Example2 is a commercially available laser marking composition marketed as a“universal” or “all-purpose” laser marking composition. The laser markswere formed using a universal 35 watt CO₂ laser. The laser settings forInventive Example 2 were 10P/25S, and for Comparative Example 2 were10P/25S. The resulting laser markings on ceramic were evaluated forluminance and color value, and the evaluations are shown below in Table3.

TABLE 3 Marking Composition L* a* b* DL* Da* Db* DE* Inventive 29.110.44 1.79 Example 2 Comparative 36.56 0.24 5.70 7.45 −0.20 3.92 8.42Example 2

As can be seen, Comparative Example 2 produced a laser mark on glassthat was 7.45 units lighter (i.e. DL*) versus Inventive Example 2.

Evaluation 4. This evaluation was performed by marking a ceramicsubstrate using Inventive Example 2 and Comparative Example 2. The lasermarks were formed using a universal 35 watt CO₂ laser. The lasersettings for Inventive Example 2 were 10P/15S, and for ComparativeExample 2 were 10P/15S. The resulting laser markings on ceramic wereevaluated for luminance and color value, and the evaluations are shownbelow in Table 4.

TABLE 4 Marking Composition L* a* b* DL* Da* Db* DE* Inventive 34.180.73 3.63 Example 2 Comparative 42.69 3.69 3.39 8.51 2.96 −0.25 9.02Example 2

As can be seen, Comparative Example 2 without the enhancer produced alaser mark on ceramic that was 8.51 units lighter (i.e. DL*) versus thelaser mark produced by Inventive Example 2 with the enhancer.

Evaluation 5. This evaluation was performed by marking a ceramicsubstrate using Inventive Example 2 and Comparative Example 2. The lasermarks were formed using a universal 35 watt CO₂ laser. The lasersettings for Inventive Example 2 were 15P/25S, and for ComparativeExample 2 were 15P/25S. The resulting laser markings on ceramic wereevaluated for luminance and color value, and the evaluations are shownbelow in Table 5.

TABLE 5 Marking Composition L* a* b* DL* Da* Db* DE* Inventive 23.920.80 1.70 Example 2 Comparative 37.38 3.08 5.77 13.46 2.28 4.07 14.25Example 2

As can be seen, Comparative Example 2 without the enhancer produced alaser mark on ceramic that was 13.46 units lighter (i.e. DL*) versus thelaser mark produced by Inventive Example 2 with the enhancer.

Evaluation 6. This evaluation was performed by marking an anodizedaluminum substrate using Inventive Example 2 and Comparative Example 2.The laser marks were formed using a universal 35 watt CO₂ laser. Thelaser settings for Inventive Example 2 were 100P/10S, and forComparative Example 2 were 100P/5S. The resulting laser markings onanodized aluminum were evaluated for luminance and color value, and theevaluations are shown below in Table 6.

TABLE 6 Marking Composition L* a* b* DL* Da* Db* DE* Inventive 36.661.62 5.36 Example 2 Comparative 50.48 2.26 12.37 13.82 0.65 7.02 15.51Example 2

As can be seen, Comparative Example 2 without the enhancer produced alaser mark on ceramic that was 13.82 units lighter (i.e. DL*) versus thelaser mark produced by Inventive Example 2 with the enhancer.

Evaluation 7. This evaluation involved the use of an inventive lasermarking composition, Inventive Example 3, including 5-15 wt % enhancer(either FeSi, SiC, FeMn), 20-25 wt % CoCrMnFe MMO pigment, 5-10 wt %mica silicate mineral, 3-8 wt % MoO₃ transition metal oxide, 1-3 wt %hydroxypropyl cellulose binder, 45-55 wt % ethanol solvent, and 2-5 wt %dispersant in the form of equal parts Anti Terra 204 and DISPERSBYK 182.

A Comparative Example 3 laser marking composition was used and comprisedcommercially available laser marking compositions marketed as“universal” or “all-purpose” laser marking compositions, including inaerosol form comprising 15-40 wt % ethanol, 15-40 wt % acetone, 10-30 wt% propane, 5-10 wt % butane; 1-5 wt % molybdenum, 1-5 wt % crystallinesilica, 1-5 wt % ethylene glycol butyl ether, and 0.1-1 wt % methylisobutyl ketone; and in paste form comprising 50-55 wt % water, 9-11 wt% molybdenum trioxide, 12-14 wt % of a mixture containing 3-5 wt %quartz, 5-7 wt % pyrophyllite, 3-5 wt % mica, and 1-1.5 wt % kaolinclay.

The substrates marked including ceramic, glass, slate, anodizedaluminum, aluminum, brass, stainless steel, thermoplastic polyurethane(TPU) polymer.

As shown in FIG. 1, proceeding clockwise from the upper left, a slatesubstrate, a ceramic substrate, and a glass substrate were marked withInventive Example 3 including 5-15 wt % FeSi enhancer under variouslaser operation parameters.

As shown in FIG. 2, proceeding clockwise from the upper left, astainless steel substrate, an aluminum substrate, an anodized aluminumsubstrate, a red dyed anodized aluminum, a brass substrate, an anodizedaluminum substrate, and an anodized aluminum substrate, were marked withInventive Example 3 including 5-15 wt % FeSi enhancer under variouslaser operation parameters.

As shown in FIG. 3, a polycarbonate plastic substrate was marked withInventive Example 3 including 5-15 wt % FeSi enhancer under variouslaser operation parameters.

As shown in FIG. 4, the top ceramic substrate was marked with InventiveExample 3 including 5-15 wt % FeSi enhancer under various laseroperation parameters, and the bottom ceramic substrate was marked withthe Comparative Example 3 under various laser operation parameters. Ascan be seen, under the same laser operation parameters, InventiveExample 3 including 5-15 wt % FeSi enhancer produced darker, morecontrasting marks than Comparative Example 3 not including the enhancer.

In particular, the following tables shows data from the markingsdepicted in FIG. 4. The inventive marks (top) and the comparative marks(bottom) were prepared using a Universal 35 watt laser, and theinventive marks were compared to the darkest comparative marks (i.e.those with the highest contrast), which were attained at 10, 15, 20power. This comparison provides a greater latitude between the markingcapabilities of the Inventive Example 3 versus the Comparative Example3.

The Delta L in Table 7 is the darkness value at a laser power of 10 anda speeds of 15/20/25. As seen, the enhanced Inventive Example 3 exhibitsa darker, more contrasting mark by an average of 11.1 units darkerversus Comparative Example 3.

TABLE 7 Example Laser Power/Speed L* a* b* DL* Da* Db* DE* ComparativeExample 3 10/15 42.96 1.99 3.62 Inventive Example 3 10/15 28.35 0.331.89 −14.61 −1.66 −1.74 14.81 Comparative Example 3 10/20 43.44 1.124.84 Inventive Example 3 10/20 32.71 0.52 2.89 −10.72 −0.6 −1.95 10.91Comparative Example 3 10/25 41.97 1.09 6.22 Inventive Example 3 10/2533.96 0.36 3.52 −8.01 −0.73 −2.7 8.48

The Delta L in Table 8 is the darkness value at a laser power of 15 anda speeds of 30/35/40. As seen, the enhanced Inventive Example 3 exhibitsa darker, more contrasting mark by an average of 12.7 units darkerversus Comparative Example 3.

TABLE 8 Example Laser Power/Speed L* a* b* DL* Da* Db* DE* ComparativeExample 3 15/30 42.81 2.42 2.95 Inventive Example 3 15/30 28.24 0.5 2.58−14.57 −1.92 −0.37 14.7 Comparative Example 3 15/35 43.32 1.7 3.74Inventive Example 3 15/35 29.54 0.6 2.93 −13.78 −1.1 −0.81 13.85Comparative Example 3 15/40 42.05 1.14 4.88 Inventive Example 3 15/4032.29 0.69 3.35 −9.76 −0.46 −1.53 9.89

The Delta L in Table 9 is the darkness value at a laser power of 20 anda speeds of 15/20/25. As seen, the enhanced Inventive Example 3 exhibitsa darker, more contrasting mark by an average of 14.2 units darkerversus Comparative Example 3.

TABLE 9 Example Laser Power/Speed L* a* b* DL* Da* Db* DE* ComparativeExample 3 20/15 51.6 1.98 10.59 Inventive Example 3 20/15 34.47 2 7.03−17.13 0.03 −3.56 17.5 Comparative Example 3 20/20 46.78 4.48 7.56Inventive Example 3 20/20 36.58 1.84 7.51 −10.2 −2.65 −0.05 10.54Comparative Example 3 20/25 46.69 5.98 7.22 Inventive Example 3 20/2531.51 1.49 5.03 −15.19 −4.49 −2.2 15.99

As shown in FIG. 5, the left glass substrate was marked with InventiveExample 3 including 5-15 wt % FeSi enhancer under various laseroperation parameters, and the right glass substrate was marked withComparative Example 3 under various laser operation parameters. As canbe seen, under the same laser operation parameters, Inventive Example 3including 5-15 wt % FeSi produced darker, more contrasting marks thanComparative Example 3.

As shown in FIG. 6, the top glass substrate was marked with InventiveExample 3 including 5-15 wt % SiC enhancer under various laser operationparameters, the bottom glass substrate was marked with Inventive Example3 including 5-15 wt % ferrous manganese enhancer under various laseroperation parameters, and the middle glass substrate was marked with thecomparative marking composition example under various laser operationparameters. As can be seen, under the same laser operation parameters,Inventive Example 3 including either SiC or Ferrous manganese enhancersproduced darker, more contrasting marks than Comparative Example 3 notincluding an enhancer.

As shown in FIG. 7, the slate substrate was marked with InventiveExample 3 including 5-15 wt % FeSi enhancer as indicated under variouslaser operation parameters, and the same slate substrate was marked asindicated with the Comparative Example 3 under various laser operationparameters. As can be seen, under the same laser operation parameters,Inventive Example 3 including 5-15 wt % FeSi produced darker, morecontrasting marks than Comparative Example 3 not including enhancers.

As shown in FIG. 8, the anodized aluminum substrate was marked withComparative Example 3 example under various laser operation parameters.As shown in FIG. 9, the anodized aluminum substrate was marked withInventive Example 3 including 5-15 wt % FeSi enhancer as indicated undervarious laser operation parameters. As can be seen between FIGS. 8 and9, under the same laser operation parameters, Inventive Example 3including 5-15 wt % FeSi enhancer produced a mark as dark as, if notdarker, than Comparative Example 3 not including enhancers.

As shown in FIG. 10, the left aluminum substrate was marked withInventive Example 3 including 5-15 wt % FeSi enhancer under variouslaser operation parameters, and the right aluminum substrate was markedwith the Comparative Example 3 under various laser operation parameters.As can be seen, under the same laser operation parameters, InventiveExample 3 including 5-15 wt % FeSi enhancer produced as dark, if notdarker, marks than the Comparative Example 3 not including enhancer.

As shown in FIG. 11, the left brass substrate was marked with InventiveExample 3 including 5-15 wt % FeSi enhancer under various laseroperation parameters, and the right brass substrate was marked with theComparative Example 3 under various laser operation parameters. As canbe seen, under the same laser operation parameters, the InventiveExample 3 including 5-15 wt % FeSi enhancer produced as dark, if notdarker, marks than Comparative Example 3 not including enhancers.

As shown in FIG. 12, the left stainless steel substrate was marked withInventive Example 3 including 5-15 wt % FeSi enhancer under variouslaser operation parameters, and the right stainless steel substrate wasmarked with the Comparative Example 3 under various laser operationparameters. As can be seen, under the same laser operation parameters,Inventive Example 3 including 5-15 wt % enhancer produced as dark, ifnot darker, marks than the Comparative Example 3 not includingenhancers.

As shown in FIG. 13, the left TPU polymer substrate was marked withInventive Example 3 including 5-15 wt % FeSi enhancer under variouslaser operation parameters, and the right TPU polymer substrate wasmarked with the Comparative Example 3 under various laser operationparameters. As can be seen, under the same laser operation parameters,Inventive Example 3 including 5-15 wt % enhancer produced darker, moredefined marks than the Comparative Example 3 not including enhancers.

As shown in FIG. 14, the left ceramic polymer substrate was marked withInventive Example 3 including 5-15 wt % FeSi enhancer at a select laseroperation parameter, and the right ceramic substrate was marked with theComparative Example 3 under the same laser operation parameter. As canbe seen, under the same laser operation parameter, Inventive Example 3including enhancer produced a darker, more defined mark than theComparative Example 3 not including enhancers. As shown in FIG. 15, whensubject to a colorimetry analysis, the mark made using Inventive Example3 was darker than the Comparative Example mark by −8.5 ΔL units. Thespectrophotometer being used to produce FIG. 15 was a Datacolor 600spectrophotometer, and the software used was CGREC, Version 2.10.

Evaluation 8. This evaluation was performed by preparing ComparativeExample 4 (FIG. 20) including only polypropylene 6600 as the polymermaterial, and Comparative Example 5 (FIG. 20) including 90 grams ofpolypropylene 6600 as the polymer material compounded with 5 grams oftalc as a filler. The components were dispersed and extruded on a DavisStandard extruder, and formed into sheets on a two roll mill. The sheetswere then marked with a YVO₄ fiber laser. As seen in FIG. 16, thepolymer material generally had a white appearance, and the laser markswere not particularly dark and therefore were not particularly distinctfrom the non-irradiated portions of the polymer material.

Inventive Examples 4, 5, 6A and 7 (FIG. 17), and Inventive Example 8(not shown) were prepared, and each included 5 grams of enhancer, 5grams of talc, and 90 grams of polypropylene 6600. Inventive Example 6B(FIG. 20) was also prepared, which included 5 grams of enhancer, 95grams of polypropylene 6600 and no talc. Inventive Example 4 includedTIN enhancer, Inventive Example 5 included B₄C enhancer, InventiveExamples 6A and 6B included Si₃N₄ enhancer, Inventive Example 7 includedSiC enhancer, and Inventive Example 8 included B₄C enhancer andadditionally included 0.5 wt % carbon black as a pigment. The componentswere dispersed and extruded on a Davis Standard extruder, and formedinto sheets on a two roll mill. As seen in FIGS. 17 and 20, thepolypropylene in Comparative Example 4 had a light (i.e. white)appearance, the polypropylene and talc in Comparative Example 5 had alight (i.e. white) appearance, the TiN enhancer and talc in InventiveExample 4 produced a dark (i.e. brown) compounded material; the B₄Cenhancer and talc in Inventive Example 5 produced a dark (i.e. black)compounded material; the Si₃N₄ enhancer and talc in Inventive Example 6Amaintained a light (i.e. white) compounded material, the Si₃N₄ enhancerand no talc in Inventive Example 6B produced a medium colored (i.e.light grey) compounded material, and the SiC enhancer and talc inInventive Example 7 maintained a light (i.e. off white) compoundedmaterial. The sheets were then marked with a YVO₄ fiber laser.

The highest contrasting laser marks in the inventive examples were thenevaluated on a DataColor spectrophotometer for L.a.b values and incomparison to non-irradiated portions of the compounded polymer material(including the enhancer) as shown below in Table 10.

TABLE 10 Portion Example Enhancer Evaluated L* a* b* DL* Da* Db* DE*Comparative n/a Non-irradiated 51.63 −1.33 −3.84 Example 4 Laser Marked47.72 −0.41 1.26 −3.9 0.92 5.1 6.49 Comparative n/a Non-irradiated 57.17−1.29 −6.06 Example 5 Laser Marked 50.09 −0.92 −2.77 −7.09 0.37 3.297.82 Inventive TiN Non-irradiated 34.13 1.25 5.39 Example 4 Laser Marked48.33 0.72 3.29 14.21 −0.52 −2.1 14.37 Inventive B₄C Non-irradiated 280.08 0.13 Example 5 Laser Marked 46.21 1.16 6.89 18.21 1.08 6.76 19.46Inventive Si₃N₄ Non-irradiated 57.96 −0.14 4.63 Example 6A Laser Marked36.69 2.49 8.13 −21.27 2.63 3.5 21.71 Inventive Si₃N₄ Non-irradiated56.05 −0.39 4.18 Example 6B Laser Marked 35.15 2.67 8.3 −20.91 3.06 4.1221.53 Inventive SiC Non-irradiated 66.55 1.31 11.02 Example 7 LaserMarked 32.24 1.81 6.04 −34.31 0.5 −4.98 34.67 Inventive B₄C—CBNon-irradiated 27.95 0.09 0 Example 8 Laser Marked 44.89 1.01 5.83 16.930.92 5.83 17.93

As seen in Table 10 and the accompanying FIG. 17, the laser marksproduced in Inventive Examples 4, 5, and 8 were lighter (positive DLvalue) than non-irradiated portions of the compounded polymer material;and the laser marks produced in Inventive Examples 6 and 7 were darker(negative DL value) than non-irradiated portions of the compoundedpolymer material. Also, the laser marks in Inventive Examples 6 and 7(which included compounded polymer material that maintained the lightappearance of the polypropylene 6600) were darker than the laser marksformed in the Comparative Examples 4 and 5 not including an enhancer.

Evaluation 9. This evaluation was performed by preparing ComparativeExample 6 including 90 grams of fluoropolymer as the polymer materialcompounded with 20 grams of glass beads as a filler. The components weredispersed in a shaker for 30 minutes with dispersion media, put througha filter to remove the dispersion media, and then drawn down into a filmwith a 3 mil bird bar to form a coating with a thickness of 0.003 inchesover a Leneta card. The coating was then air dried. The films weremarked with a YVO₄ fiber laser. As seen in FIG. 18, the polymer materialgenerally had a white appearance, and the laser marks were notparticularly dark and therefore were not particularly distinct from thenon-irradiated portions of the polymer material.

Inventive Examples 9-12 were also prepared, each of which included 10grams of enhancer, 90 grams of fluoropolymer (Super Shield from ShieldProducts Inc. of Doral, Fla., USA), and 20 grams of glass beads as afiller. Inventive Example 9 include SiC enhancer, Inventive Example 10included Si₃N₄ enhancer, Inventive Example 11 included B₄C enhancer, andInventive Example 12 included MoSi₂ enhancer. The components weredispersed in a shaker for 30 minutes with dispersion media, put througha filter to remove the dispersion media, and then drawn down into a filmwith a 3 mil bird bar to form a coating with a thickness of 0.003 inchesover a Leneta card. The coating was then air dried. As seen in FIG. 19,the SiC enhancer in Inventive Example 9 and the Si₃N₄ enhancer inInventive Example 10 both produced light (i.e. off white) films thatwere only slightly darker than Comparative Example 6, and the B₄Cenhancer in Inventive Example 11 and the MoSi₂ enhancer in InventiveExample 12 both produced dark (i.e. black) films. The sheets were thenmarked with a YVO₄ fiber laser.

The highest contrasting laser marks in Inventive Examples 9-12 were thenevaluated on a DataColor spectrophotometer for L.a.b values and incomparison to non-irradiated portions of the film as shown below inTable 11.

TABLE 11 Portion Example Enhancer Evaluated L* a* b* DL* Da* Db* DE*Inventive SiC Non-irradiated 67.52 1.7 12.46 Example 9 Laser Marked58.81 2.11 12.5 −8.71 0.42 0.04 8.72 Inventive Si₃N₄ Non-irradiated 64−0.61 6.27 Example 10 Laser Marked 56.71 2.9 13.88 −7.29 3.51 7.61 11.11Inventive B₄C Non-irradiated 35.5 −0.15 0.75 Example 11 Laser Marked54.43 0.08 1.78 18.93 0.23 1.03 18.95 Inventive MoSi₂ Non-irradiated28.69 −0.5 −0.91 Example 12 Laser Marked 40.6 −0.42 −0.52 11.91 0.090.39 11.92

As seen in Table 11 and the accompanying FIG. 19, the laser marksproduced in Inventive Examples 9 and 10 were darker (negative DL value)than non-irradiated portions of the compounded polymer material; and thelaser marks produced in Inventive Examples 11 and 12 were lighter(positive DL value) than non-irradiated portions of the compoundedpolymer material. Also, the laser marks in Inventive Examples 9 and 10(which had compounded polymer material that maintained the lightappearance of the fluoropolymer) were darker than the laser marks formedin the Comparative Example 6 not including an enhancer.

As will be appreciated, the inventive marking compositions provideimproved markings on a variety of substrates over the markingcompositions of the comparative examples, and therefore the inventivemarking compositions truly are universal or all-purpose markingcompositions that can provide improved laser marks on a variety ofsubstrates as compared to conventional marking compositions, whichprovide satisfactory marks on only a limited number of substrates (e.g.metal) and therefore cannot be considered universal or all-purposemarking compositions.

It will be appreciated that various of the above-disclosed and otherfeatures and functions, or alternatives or varieties thereof, may bedesirably combined into many other different systems or applications.Also that various presently unforeseen or unanticipated alternatives,modifications, variations or improvements therein may be subsequentlymade by those skilled in the art which are also intended to beencompassed by the following claims.

The invention claimed is:
 1. A laser marking compounded polymer materialcomprising a polymer material compounded with an enhancer, wherein: theenhancer is included at 2-20 wt % of the compounded polymer material,and is selected from the group consisting of FeMn, CaSi, Cu₅Si, FeSi,Fe₅Si₂, MgFeSi, MnSi₂, MoSi₂, Ni₂Si, TiSi₂, ZrSi₂, WSi₂, YSi, Al₄C₃,CaC₂, Fe₃C, Fe₇C₃, Fe₂C, LaC₂, Mg₂C, Mg₂C₃, Ta₄C₃, YC₂, MoN, Mo₂N,Si₃N₄, and combinations thereof; upon exposing an irradiated portion ofthe compounded polymer material to laser radiation, the irradiatedportion absorbs the laser radiation, increases in temperature and formsa mark having a luminance, color value, or degrees of opacity thatprovides visual contrast with a non-irradiated portion of the compoundedpolymer material; a lightness value difference (ΔL) between the mark andthe non-irradiated portion has an absolute value of at least 5; and thelightness value difference between the mark and the non-irradiatedportion is greater than if the polymer material did not include theenhancer.
 2. The compounded polymer material according to claim 1,further including a mixed metal oxide pigment at 5-35 wt % of thecompounded polymer material.
 3. The compounded polymer materialaccording to claim 2, wherein the compounded polymer material furtherincludes glass beads, the enhancer is included at 10 parts by weight,the polymer is included at 90 parts by weight, and the glass beads areincluded at 20 parts by weight.
 4. The compounded polymer materialaccording to claim 1, wherein the polymer material comprises one or moreof polyethylene, polypropylene, polystyrene, polyvinyl chloride,synthetic rubber, phenol formaldehyde resin, neoprene, nylon,polyacrylonitrile, PVB, silicone, fluoropolymers, acrylics,polycarbonates, and ethylene vinyl acetate.
 5. The compounded polymermaterial according to claim 4, wherein the polymer material ispolypropylene.
 6. The compounded polymer material according to claim 5,wherein the compounded polymer material is in sheet form.
 7. Thecompounded polymer material according to claim 6, further comprising1-15 wt % talc.
 8. The compounded polymer material according to claim 1,wherein the polymer material is a fluoropolymer.
 9. The compoundedpolymer material according to claim 8, wherein the compounded polymermaterial further includes 5-20 wt % glass beads.
 10. The compoundedpolymer material according to claim 9, wherein the compounded polymermaterial is coated on a substrate.
 11. A method of producing lasermarks, comprising: providing a polymer material and an enhancer selectedfrom the group consisting of FeMn, CaSi, Cu₅Si, FeSi, Fe₅Si₂, MgFeSi,MnSi₂, MoSi₂, Ni₂Si, TiSi₂, ZrSi₂, WSi₂, YSi, Al₄O₃, CaC₂, Fe₃C, Fe₇C₃,Fe₂C, LaC₂, Mg₂C, Mg₂C₃, Ta₄C₃, YC₂, MoN, Mo₂N, Si₃N₄, and combinationsthereof; compounding the polymer material and the enhancer to produce acompounded polymer material including 2-20 wt % of the enhancer; formingthe compounded polymer material into an article having a desiredconfiguration; irradiating an irradiated portion of the article withlaser radiation such that the irradiated portion absorbs the laserradiation, increases in temperature, and forms a mark in the articlethat has a luminance, color, and/or degree of opacity that contrastswith a non-irradiated portion of the article, wherein a lightness valuedifference (ΔL) between the mark and the non-irradiated portion has anabsolute value of at least 5; and the lightness value difference betweenthe mark and the non-irradiated portion is greater than if the polymermaterial did not include the enhancer.
 12. The method according to claim11, wherein the compounded polymer material further includes 5-35 wt %mixed metal oxide pigment.
 13. The method according to claim 12, whereinthe compounded polymer material further includes glass beads, theenhancer is included at 10 parts by weight, the polymer is included at90 parts by weight, and the glass beads are included at 20 parts byweight.
 14. The method according to claim 11, wherein the polymermaterial comprises one or more of polyethylene, polypropylene,polystyrene, polyvinyl chloride, synthetic rubber, phenol formaldehyderesin, neoprene, nylon, polyacrylonitrile, PVB, silicone,fluoropolymers, acrylics, polycarbonates, and ethylene vinyl acetate.15. The method according to claim 14, wherein the polymer material ispolypropylene.
 16. The method according to claim 15, wherein the articleis a sheet of the compounded polymer material.
 17. The method accordingto claim 16, wherein the compounded polymer material further comprises1-15 wt % talc.
 18. The method according to claim 11, wherein thepolymer material is a fluoropolymer.
 19. The method according to claim18, wherein the compounded polymer material further includes 5-20 wt %glass beads.
 20. The method according to claim 19, wherein the articleis a coating of the compounded polymer material on a substrate.